In the application field of the current LEDs, most of the LED chips are now developing towards the form of flip chips in response to the trend of products. Also in response to the trend of miniaturization, packaging structures of chip scale package (CSP) have been developed. That is, the area of the packaging structure should not be exceed the area of the LED chip too much (e.g., being no more than 1.3 times of the area of the LED chip). With this limitation in the area, it is difficult to dispose an electric static discharge (ESD) protection element beside the LED chip in the conventional CSP packaging structures, so the LED chip is likely to be damaged due to electric static discharge.
Additionally, the flip chips may also be bonded with a substrate in various die bonding manners. For example, the electrical connection between the chip and the substrate is achieved through, e.g., direct bonding, eutectic bonding, golden ball bonding, or conductive adhesives bonding.
Different from the traditional packaging technology, the flip chip packaging can not only reduce the size of the packaged chip but also reduce the transmission distance of electronic signals between the chip and the substrate to achieve advantages such as low signal interference and electrical stability. Moreover, to enhance the machinability of the frame and to achieve a good bonding between the frame and pins disposed below the frame, the frame usually adopts the epoxy molding compound (EMC) as a main material thereof.
As shown in a schematic perspective view of a frame 100 according to the prior art in FIG. 1, the frame 100 comprises a housing 120, a lead 130, a gap filler 140 and a light transmitting encapsulant 150. The lead 130 has a first electrode portion 131 and a second electrode portion 132 adjacent to each other, there is a gap 133 between the first electrode portion 131 and the second electrode portion 132, the gap filler 140 is disposed within the gap 133, the LED 110 may be adapted to be fixed and electrically connected with the first electrode portion 131 and the second electrode portion 132, and the light transmitting encapsulant 150 may be adapted to fill the housing 120 and cover the LED chip 110.
However, before the frame 100 is subjected to the high-temperature die bonding stage, as shown in FIG. 2A, the gap filler 140 almost fills the whole gap 133 before the gap filler 140 is under the high temperature. After the frame 100 is subjected to a high-temperature bonding stage such as the direct boding, the golden ball bonding or the eutectic bonding, as shown in FIG. 2B, an expanded volume 142 of the gap filler 140 generated under the high temperature will protrude from the gap 133 due to the insufficient accommodating space within the gap 133. Therefore, a bottom surface 112 of the LED chip 110 will be in contact with the protruding expanded volume 142 of the gap filler 140, which results in the damage of the inner structure of the LED chip 110 or the bonding surface 134 between the bottom surface 112 of the LED chip 110 and the lead 130 due to the stress from the protruding expanded volume.
Additionally, in the conventional light emitting device, the LED chip is arranged on one surface of a substrate and then emits light towards the direction away from the surface. Under this arrangement, almost all the light rays emitted by the LED chip propagate towards the same direction and only few light rays (or no light ray) reach/reaches the other side of the substrate, so the overall light emitting range of the light emitting device is not more than 180°. In other words, the light emitting device cannot provide omni-directional light effect. Therefore, such a light emitting device is limited in application; that is, the light emitting device is unsuitable for use in occasions requiring uniform lighting.
In view of the aforesaid problems, the present disclosure provides a novel LED packaging structure, which can comprise an ESD protection element within the size requirements of chip-level packaging. Additionally, the present disclosure also provides a novel frame, which can overcome the problem resulting from the volume expansion of the gap filler and is adapted to support the LED packaging structure to form a light emitting device. The present disclosure further provides a novel light emitting device, which can accommodate with the aforesaid LED packaging structure and has the omni-directional light emitting effect.